Refactor clippy::match_ref_pats to check for multiple reference patterns

[1nF0rmed]

fixes #7740

When there is only one pattern, to begin with, i.e. a single deref(&), then in such cases we suppress clippy::match_ref_pats.
This is done by checking the count of the reference pattern and emitting clippy::match_ref_pats when more than one pattern is present.

Removed certain errors in the stderr tests as they would not be triggered.

changelog: Refactor clippy::match_ref_pats to check for multiple reference patterns

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @llogiq (or someone else) soon.

Please see the contribution instructions for more information.

[llogiq]

Cool stuff! The only downside I see is that some test cases are now effectively disabled. Would you be OK with changing them so they apply again and adding one or two new tests that show single ref patterns are not linted?

[1nF0rmed]

@llogiq Thank you! I can update the test cases but if I'm not wrong,
given the change, errors in tests/ui/match_expr_like_matches_macro.stderr will not occur

Let me know if I can approach this differently

[llogiq]

I'm only talking about the lint's own tests. To make the error re-occur, you may need an enum with more than two cases.

[1nF0rmed]

Given that we want to use an enum with more than two cases, would something like this work?

    fn issue_7740() {
        // Should trigger lint
        match foobar_variant!(0) {
            &FooBar::Foo => println!("Foo"),
            &FooBar::Bar => println!("Bar"),
            &FooBar::FooBar => println!("FooBar"),
            _ => println!("Wild"),
        }
        
        // This shouldn't trigger
        if let &FooBar::BarFoo = foobar_variant!(3) {
            println!("BarFoo");
        } else {
            println!("Wild");
        }
    }

[llogiq]

Thank you! @bors r+

[bors]

📌 Commit 1080f6c has been approved by llogiq

[bors]

⌛ Testing commit 1080f6c with merge 9205e3d...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: llogiq
Pushing 9205e3d to master...